Dynamic contour tonometry in keratoconus and postkeratoplasty eyes.

PURPOSE: To compare the performance of dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in measuring intraocular pressure in eyes with irregular corneas. METHODS: GAT and DCT measures were taken in 30 keratoconus and 29 postkeratoplasty eyes of 35 patients after pachymetry and corneal topography. Regression and correlation analyses were performed between both tonometry methods and between tonometry methods and corneal parameters. Bland-Altman plots were constructed. RESULTS: DCT values were significantly higher than GAT values in both study groups: +4.1 +/- 2.3 mm Hg (mean +/- SD) in keratoconus and +3.1 +/- 2.5 mm Hg after keratoplasty. In contrast to DCT, GAT values were significantly higher in postkeratoplasty eyes than in keratoconus. The correlation between the 2 tonometry methods was moderate in keratoconus (Kendall correlation coefficient, tau = 0.34) as well in postkeratoplasty eyes (tau = 0.66). The +/-1.96 SD span of the DCT-GAT differences showed a considerable range: -0.42 to +8.70 mm Hg in keratoconus and -1.87 to +7.98 mm Hg in postkeratoplasty eyes. In the keratoconus group, neither DCT nor GAT correlated significantly with any of the corneal parameters. In the postkeratoplasty group, both DCT and GAT measures showed a moderate positive correlation with corneal steepness, but only DCT had a significant negative correlation with the central corneal thickness (tau = -0.33). CONCLUSIONS: DCT measured significantly higher intraocular pressures than GAT in keratoconus and postkeratoplasty eyes. DCT and GAT measures varied considerably, and DCT was not less dependent on biomechanical properties of irregular corneas than GAT.

Determination of microdot stromal degenerations within corneas of long-term contact lens wearers by confocal microscopy.

PURPOSE: To ascertain whether a relationship exists between the presence of microdot deposits within the corneal stroma of long-term contact lens wearers as seen by confocal microscopy and the contact lens wear time, material, or other patient variables. METHODS: Thirty-six myopic patients with a 15- to 43-year history of hard, rigid gas-permeable, or soft hydrogel contact lens wear and 12 age-matched emmetropic or spectacle-corrected myopic volunteers were included in this study. The numerical density and size of microdot deposits within the anterior, mid, and posterior stroma were determined with the confocal microscope, and the data were subjected to multiple regression statistical analysis. RESULTS: Microdot deposits were encountered throughout the entire depth of the corneal stroma in all contact lens wearers. None of the control subjects showed microdot deposits. The numerical densities and the size range of microdots were similar in each of the stromal layers (anterior, mid, and posterior), with total mean values (+/- SD) for each parameter being 65.1 x 10(3) +/- 26.9 x 10(3) dots/mm (range, 21.4 x 10(3) to 121.1 x 10(3) dots/mm) and 3.04 +/- 0.92 microm (range, 1.5-5.0 microm), respectively. CONCLUSIONS: Microdot deposits may represent granules of lipofuscinlike material within the corneal stroma of long-term contact lens wearers, formed as a result of chronic oxygen deprivation and chronic microtrauma to the cornea. No one in the control group showed microdot deposits. Among the independent variables, soft contact lens wear time had the most profound influence on numerical microdot density and size in our statistical equations.